Bulk polymerization propylene

The kinetic models for the gas phase polymerization of propylene in semibatch and continuous backmix reactors are based on the respective proven models for hexane slurry polymerization ( ). They are also very similar to the models for bulk polymerization. The primary difference between them lies in the substitution of the appropriate gas phase correlations and parameters for those pertaining to the liquid phase. 

The propylene oxide complex not only dissociated into its components but also transformed to either an oligomer or a polymer of propylene oxide when it was allowed to stand in solution. This transformation could be followed by H-NMR techniques with the use of a-deuterated propylene oxide instead of the non-deuterated one. Its rate depended on the nature of solvent and on the temperature. This experimental result implies that the monomer liberated by dessociation of the complex is polymerized by the catalyst, that only a minute fraction of the organozinc component of the complex actually acts as a catalyst for polymerization, and that the rate of propagation is far faster than that of initiation. These implications together with the evidence that coordination of the monomer to the catalyst is a prerequisite for the stereospecific polymerization led us to the detailed studies of the bulk polymerization, that is, the polymerization of propylene oxide in propylene oxide solution. 

Bulk Polymerization of Propylene Oxide by EtZnNBu ZnEt (90)... 

Table 11. BulK polymerization of propylene oxide by EtZnNBu ZnEt at 80° C...

Table II. Effects of Glyme and Zinc Chloride on Activity of Zinc Hexacyanocobaltate for Bulk Polymerization of Propylene Oxide...

Activities of the catalysts for polymerizing propylene oxide in bulk at 30° C were compared on the basis of the weight of polymer formed per weight of catalyst per unit time. Zinc hexacyanocobaltate itself was a fairly active catalyst, giving 300 grams of polymer per gram of... 

Figure 4. Typical time-conversion plot. Bulk polymerization of propylene oxiae with Znx[Fe(CN)e]7 acetone ZnCU (020 wt %)...

Table III. Bulk Polymerization of Propylene Oxide with Zinc Hexacyanocobaltate-Glyme-Zinc Chloride Catalyst at 30° C...

Figure 5. Variation of intrinsic viscosity with conversion during bulk polymerization of propylene oxide with Zns[Co(CN)e]2 glyme ZnCU (0.01 wt %) at 30°C...

Conditions bulk polymerization in 1 liter of liquid propylene at 70°C, Al/Zr molar ratio = 15000. The results illustrate the broad range of attainable product properties (155). 

The application of this method to the study of THF polymerization on BF3 + propylene oxide (bulk polymerization, T- 20 °C) has made it possible to establish the following facts in this system the active centers are deactivated in accordance with the first order reaction k A = 1.9 x 10 4 s 1). Propylene oxide is consumed... 

Propylene, catalyst, cocatalyst, donor, hydrogen, and comonomer (for random copolymers) are fed into the loop reactor propylene is used as the polymerization medium (bulk polymerization). The loop reactor is designed for supercritical conditions and operates at 80-100°C and 50-60 bar. The propylene/polymer mixture exits the loop reactor and is sent to a fluidized-bed, gas-phase reactor, where propylene is consumed in polymerization. This reactor operates at 80-100°C and 25-35 bar. Fresh propylene, hydrogen and comonomer (in case of random copolymers) are fed into the reactor. After removing hydrocarbon residuals, the polymer powder is transferred to extrusion. 

Figure 11. Polymerization conditions Tp = 60 °C MAO, Al/Zr = 1000 bulk polymerization of propylene.

The anionic polymerization of propylene oxide initiated by potassium alkoxide or hydroxide occurs predominantly (95%) by cleavage of the O-CH2 bond. For bulk polymerization at 80 °C, approximately 4% head-to-head placements occur. However, there is no stereocontrol in this alkoxide-initiated ring opening and the resulting polymer is nontactic [140]. 

Rexene Co. and Philips Petroleum Co. first developed the bulk polymerization process with the first-generation TiCU catalyst [8,11,70]. It was then commercialized by Dart Industries in 1964. The reactor feed contains 10-30% propylene in the liquid phase. A mixture of hexane and isopropanol was employed for the removal of catalyst residue as well as the amorphous polypropylene. The process step of removing residual catalyst was later eliminated after the high-efficiency catalyst was adopted, constituting the so-called liquid pool process. Subsequently, Philips and Sumitomo companies further developed the liquid-phase polymerization process. This process enhances the reaction rate, catalyst efficiency, monomer conversion, and therefore results in high productivity. It also eliminates the need for solvent recovery and reduces environmental pollution. However, the process is somewhat complicated by the unreacted monomer, which has to be first vaporized and then liquefied before it is reused. The reaction vessel must be designed to operate under high pressures. In most cases, this process employs autoclaves for batch operation and tubular reactors for continuous operation. 

It could also be demonstrated that a very rapid passing of these stages occurs when the polymerization is carried out in liquid propylene [45 7] this means that the industrially important bulk polymerization can also be exactly described by this polymer growth and particle expansion model [41-43, 48]. 

Later, bulk polymerization processes were developed where either liquid propylene was used as the only diluent in a loop reactor or was permitted to boil out to remove the heat of reaction. The latter was conducted in stirred vessels with vapor space at the top. 

By far the most commonly used PP-process is Montell s Spheripol Process. The first reaction stage consists of one or two tubular loop reactors where bulk polymerization of homopolymers, random and terpol5nners is carried out in liquid propylene. The prepolymerized catalyst, liquid propylene, hydrogen for controlling molecular weight and eventually comonomers are continuously fed into the reactor in which polymerization takes place at temperatures of 60-80°C and pressures of 35-40 bar. The tubular configuration enables a perfect heat transfer and control of the reaction temperature. 

A more recent set of experiments favors the alternating mechanism. If polymerizations are conducted in dilute monomer (10% by volume in toluene), the melting temperatures and [mmmm] fractions exceed those obtained from bulk polymerizations. For example, Tm = 135 °C and [mmmm] = 88.8% are obtained in 10% monomer solution as compared to Tm = 129 °C and [mmmm] = 78.0% in neat monomer at the same Tp(40 °C). In addition, under these dilute conditions, [mmmm] is found to increase from 82.2% to 89.4% as the polymerization temperature increases over the range of 0-60 °C. A similar effect was reported with 2 bar of propylene monomer in toluene the [mmmm] fraction increased from 83.5% to 87.7% as Tp increased from 10 to 50 These results are consistent with an alternating mechanism that increasingly yields to a site epimerization mechanism as the monomer concentration decreases or the polymerization temperature increases. This conclusion is... 

A vanadium complex ligated by a tridentate thiobisphenoxy group (6, Figure 6.1) was reported by scientists at Sumitomo Chemical to produce isotactic polypropylene with 68% mm and a Tm of 138 °C (MAO, 20 °C, 1 h, propylene bulk polymerization). ... 

Several polymerization processes are carri out in single liquid phase systems. The most widespread process of this type is the high pressure polymerization of ethylene (for "low-density" polyethylene). Other well Imown examples are the newest high temperature versions of processes for the polymerization of ethylene with Ziegler-type catalysts (for "high density" polyethylene), the preparation of some synthetic rubbers (polybutadiene, polyisoprene, ethylene-propylene co- and ter-polymers), the "bulk" polymerization of styrene, etc. All these processes have in common that the reaction product is a polymer melt or solution, that is relatively viscous. Since at the same time the intrinsic reaction rates are usually quite high, the conversion rates are often limited by diffusion. These processes are usually carried out in stirred reactors, for which the effects of micro-mixing have to be taken into account. 

Polymerizations. The metallocene derivatives and cocatalyst were precontacted for 20 minutes in toluene solutions containing 10.7 wt-% of Schering s MAO with MW 1,300. in bulk polymerizations, the catalyst solution and liquid propylene were added sequentially to a magnedrive, packless Zipperclave at room temperature and prepolymerized on heating the reactor contents, with stirring, to the reaction temperature within 3 minutes of monomer addition. 

The suggestion of a dual rate law with first and second order dependencies of r/m on propylene concentration (Figure 6) is consistent with the residual 1.3% m placements in bulk polymerizations at 65°C being at least partially due to low concentrations of intermediates with two propylene molecules coordinated simultaneously on both sides of the growing chain. 

Common to all polymerization units is the bulk polymerization section for homo- and random- copolymers. This bulk polymerization employs tubular loop reactors filled with liquid propylene, which is continuously fed the catalyst and hydrogen for molecular... 

In modern PP suspension processes the polymerization of homopolymers and random copolymers takes place in liquid propylene (bulk polymerization). The polymerization can be continued in one or several gas phase reactors, especially when impact copolymer is produced. 

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